Sanshools are a main ingredient of a crude drug, “Zanthoxylum Fruit”. In recent years, HαS (hydroxy-α-sanshool) has been reported to have effects such as stimulations of TRPV1 and TRPA1 and is now in the spotlight of the medicinal chemical field.
Sanshools including HαS have an unstable structure due to a triene moiety. Therefore, it has been difficult to constantly produce and supply sanshool as a pure substance. Conventionally, sanshools have been isolated and purified from an extract of sanshoo as a raw material by silica gel and ODS column chromatography.
Total syntheses of HαS and HβS (hydroxy-β-sanshool) have not been reported in the past, but a total synthesis of α-sanshool as an analogue thereof has been reported (see Non-Patent Documents 1 and 2). Methods described in the Non-Patent Documents 1 and 2 are both those for forming a triene moiety by a Wittig reaction.